<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2017 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
and with the Back-Cover Texts as in (a) below.

(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual.  Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom." -->
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
<head>
<title>Debugging with GDB: ABI</title>

<meta name="description" content="Debugging with GDB: ABI">
<meta name="keywords" content="Debugging with GDB: ABI">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Controlling-GDB.html#Controlling-GDB" rel="up" title="Controlling GDB">
<link href="Auto_002dloading.html#Auto_002dloading" rel="next" title="Auto-loading">
<link href="Numbers.html#Numbers" rel="prev" title="Numbers">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.indentedblock {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
div.smalllisp {margin-left: 3.2em}
kbd {font-style:oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nocodebreak {white-space:nowrap}
span.nolinebreak {white-space:nowrap}
span.roman {font-family:serif; font-weight:normal}
span.sansserif {font-family:sans-serif; font-weight:normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="ABI"></a>
<div class="header">
<p>
Next: <a href="Auto_002dloading.html#Auto_002dloading" accesskey="n" rel="next">Auto-loading</a>, Previous: <a href="Numbers.html#Numbers" accesskey="p" rel="prev">Numbers</a>, Up: <a href="Controlling-GDB.html#Controlling-GDB" accesskey="u" rel="up">Controlling GDB</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Configuring-the-Current-ABI"></a>
<h3 class="section">22.6 Configuring the Current ABI</h3>

<p><small>GDB</small> can determine the <em>ABI</em> (Application Binary Interface) of your
application automatically.  However, sometimes you need to override its
conclusions.  Use these commands to manage <small>GDB</small>&rsquo;s view of the
current ABI.
</p>
<a name="index-OS-ABI"></a>
<a name="index-set-osabi"></a>
<a name="index-show-osabi"></a>
<a name="index-Newlib-OS-ABI-and-its-influence-on-the-longjmp-handling"></a>

<p>One <small>GDB</small> configuration can debug binaries for multiple operating
system targets, either via remote debugging or native emulation.
<small>GDB</small> will autodetect the <em>OS ABI</em> (Operating System ABI) in use,
but you can override its conclusion using the <code>set osabi</code> command.
One example where this is useful is in debugging of binaries which use
an alternate C library (e.g. <small>UCLIBC</small> for <small>GNU</small>/Linux) which does
not have the same identifying marks that the standard C library for your
platform provides.
</p>
<p>When <small>GDB</small> is debugging the AArch64 architecture, it provides a
&ldquo;Newlib&rdquo; OS ABI.  This is useful for handling <code>setjmp</code> and
<code>longjmp</code> when debugging binaries that use the <small>NEWLIB</small> C library.
The &ldquo;Newlib&rdquo; OS ABI can be selected by <code>set osabi Newlib</code>.
</p>
<dl compact="compact">
<dt><code>show osabi</code></dt>
<dd><p>Show the OS ABI currently in use.
</p>
</dd>
<dt><code>set osabi</code></dt>
<dd><p>With no argument, show the list of registered available OS ABI&rsquo;s.
</p>
</dd>
<dt><code>set osabi <var>abi</var></code></dt>
<dd><p>Set the current OS ABI to <var>abi</var>.
</p></dd>
</dl>

<a name="index-float-promotion"></a>

<p>Generally, the way that an argument of type <code>float</code> is passed to a
function depends on whether the function is prototyped.  For a prototyped
(i.e. ANSI/ISO style) function, <code>float</code> arguments are passed unchanged,
according to the architecture&rsquo;s convention for <code>float</code>.  For unprototyped
(i.e. K&amp;R style) functions, <code>float</code> arguments are first promoted to type
<code>double</code> and then passed.
</p>
<p>Unfortunately, some forms of debug information do not reliably indicate whether
a function is prototyped.  If <small>GDB</small> calls a function that is not marked
as prototyped, it consults <kbd>set coerce-float-to-double</kbd>.
</p>
<dl compact="compact">
<dd><a name="index-set-coerce_002dfloat_002dto_002ddouble"></a>
</dd>
<dt><code>set coerce-float-to-double</code></dt>
<dt><code>set coerce-float-to-double on</code></dt>
<dd><p>Arguments of type <code>float</code> will be promoted to <code>double</code> when passed
to an unprototyped function.  This is the default setting.
</p>
</dd>
<dt><code>set coerce-float-to-double off</code></dt>
<dd><p>Arguments of type <code>float</code> will be passed directly to unprototyped
functions.
</p>
<a name="index-show-coerce_002dfloat_002dto_002ddouble"></a>
</dd>
<dt><code>show coerce-float-to-double</code></dt>
<dd><p>Show the current setting of promoting <code>float</code> to <code>double</code>.
</p></dd>
</dl>

<a name="index-set-cp_002dabi"></a>
<a name="index-show-cp_002dabi"></a>
<p><small>GDB</small> needs to know the ABI used for your program&rsquo;s C<tt>++</tt>
objects.  The correct C<tt>++</tt> ABI depends on which C<tt>++</tt> compiler was
used to build your application.  <small>GDB</small> only fully supports
programs with a single C<tt>++</tt> ABI; if your program contains code using
multiple C<tt>++</tt> ABI&rsquo;s or if <small>GDB</small> can not identify your
program&rsquo;s ABI correctly, you can tell <small>GDB</small> which ABI to use.
Currently supported ABI&rsquo;s include &ldquo;gnu-v2&rdquo;, for <code>g++</code> versions
before 3.0, &ldquo;gnu-v3&rdquo;, for <code>g++</code> versions 3.0 and later, and
&ldquo;hpaCC&rdquo; for the HP ANSI C<tt>++</tt> compiler.  Other C<tt>++</tt> compilers may
use the &ldquo;gnu-v2&rdquo; or &ldquo;gnu-v3&rdquo; ABI&rsquo;s as well.  The default setting is
&ldquo;auto&rdquo;.
</p>
<dl compact="compact">
<dt><code>show cp-abi</code></dt>
<dd><p>Show the C<tt>++</tt> ABI currently in use.
</p>
</dd>
<dt><code>set cp-abi</code></dt>
<dd><p>With no argument, show the list of supported C<tt>++</tt> ABI&rsquo;s.
</p>
</dd>
<dt><code>set cp-abi <var>abi</var></code></dt>
<dt><code>set cp-abi auto</code></dt>
<dd><p>Set the current C<tt>++</tt> ABI to <var>abi</var>, or return to automatic detection.
</p></dd>
</dl>

<hr>
<div class="header">
<p>
Next: <a href="Auto_002dloading.html#Auto_002dloading" accesskey="n" rel="next">Auto-loading</a>, Previous: <a href="Numbers.html#Numbers" accesskey="p" rel="prev">Numbers</a>, Up: <a href="Controlling-GDB.html#Controlling-GDB" accesskey="u" rel="up">Controlling GDB</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>



</body>
</html>
